An engine exhaust gas treatment system in the prior art usually comprises a urea tank, a urea pump for extracting a urea solution from said urea tank and a nozzle connected to said urea pump. Said nozzle is used for injecting atomized urea into an exhaust pipe of an engine to purify exhaust gas.
However, in practical applications, bubbles are often produced in a system pipeline, and the working efficiency and metering accuracy of urea solution pumping of said urea pump would be reduced due to the bubbles.